Heat Pump Water Heater

ABSTRACT

A heat pump water heater includes a heat pump which generates a hot refrigerant and a water tank for water to be heated. The water tank includes a surrounding wall which is preferably cylindrical and a bottom portion. An inner sleeve is located in the bottom portion of the water tank, and is spaced from the bottom portion and an adjacent portion of the surrounding wall of the water tank, whereby a passageway is provided about the inner sleeve. The inner sleeve also includes an opening at a bottom thereof. A circulation system puts the heated refrigerant in a heat exchange relationship with the water in the passageway, causing heating of the water therein and, due to natural convection, movement of the heated water to a higher position in the water tank and a resultant flow of cooler water into the passageway through the bottom opening of the inner sleeve.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional application61/323,584, filed Apr. 13, 2010 and entitled Heat Pump Water Heater(which is hereby incorporated by reference).

BACKGROUND OF THE INVENTION

The heating of water for residential usage is generally 30% to 40% ofthe monthly energy costs of a traditional household. With a renewedinterest in improving energy efficiency and the saving of fossil fuels,new innovations in water heaters are being developed to increaseefficiency. The latest technology in water heater design is oftenreferred to as, “all in one heat pump water heaters”. Water heater ofthis design include small heat pumps with attached storage tanks. Thisdesign currently provides the most efficient method of heating water forresidential or commercial applications.

There are many methods of affecting heat transfer to water from a heatpump. Although almost all heat pump water heaters are more efficientthat conventional resistant heat water heaters, each design has its ownassets (and liabilities) in terms of efficiency and longevity. One priorart design involves the use of a copper tube coiled within a waterstorage tank that transfers heat from the compressor refrigerant flowingthrough the copper tube to the potable water in the tank to heat thewater in the tank. This type of internal tube heat transfer is fairlyefficient, however the single tube creates a safety hazard if there iscorrosion or rupture in the tube causing contamination of the potablewater by the refrigerant. Another variation of this prior art toovercome the contamination makes use of a double wall refrigerant tubewhich is also coiled within the potable water. The double wall tube isdesigned to protect the potable water even if there is a rupture ineither tube. Any rupture in either tube generally causes the unit toshut down; and since the refrigerant coils are not replaceable, such arupture renders the unit a total loss.

Internal heat transfer tubes also have a great likelihood of attractingminerals from contact with potable water. This contact can lead tocorrosion, and calcium and mineral build up on the tubes, whichdecreases the heat transfer efficiency of such internal tubes.

Another prior art method used to overcome the contamination problem isto have the heat transfer take place outside of the tank, within theheat pump unit. These types of units generally avoid the contaminationproblems, but are not as efficient and cause the incoming cold water tomix with the hot water in the tank, lowering the overall temperature inthe tank as the water is being heated. This method is also not veryefficient due to the amount of heated surface area upon which the tankwater can come into contact with the cold water, and the reducedefficiency of the heat transfer between the heat coils and the outertank.

The present invention departs from the traditional heap pump waterheater designs, and is an improved way to transfer heat from the heatpump to the water with improved efficiency and reduced risk ofcontamination and calcium build up.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing disadvantages noted to be inherent in the priorheat pump water heater designs, the present invention is designed to bevery efficient in the heating of water and to completely eliminated thechance of the potable water being contaminated by the heat transferprocess.

Thus, in accordance with the present invention, there is provided a heatpump water heater including a heat pump which generates a hotrefrigerant and a water tank in which water to be heated is contained.The water tank includes a lower portion defined by a bottom wall and asurrounding wall which is preferably cylindrical and thus which extendsupwardly from bottom wall. Also provided is an inner sleeve located inthe lower portion of the water tank. This inner sleeve is spaced fromthe bottom wall and an adjacent portion of the surrounding wall, wherebya passageway is provided about the inner sleeve. The inner sleeve alsoincludes an opening at a bottom thereof. Finally, a circulation systemis provided by which the heated refrigerant from the heat pump is put ina heat exchange relationship with the water in the passageway, causingheating of the water in the passageway and, due to natural convection,movement of the heated water to a higher position in the water tank anda resultant flow of cooler water into the passageway through the bottomopening of the inner sleeve.

In a preferred embodiment, the circulation system includes tubing whichreceives the hot refrigerant from the heat pump and which serves to heatthe water in the passageway. In this preferred embodiment, the watertank also includes grooves in an outside surface of the adjacent portionof the surrounding wall of the water tank in which the tubing islocated. The tubing is disposed in a spiral pattern in the grooves onthe outside surface of the water tank. In an alternative embodiment, theoutside surface of the water tank is smooth and the tubing is spirallywound and preferably also in contact therewith.

For better efficiency, the tubing is preferably provided with an outerheat transfer promoting covering; and as desired, an outer protectivecovering which may as well promote heat transfer.

If desired, the inner sleeve can be provided with a spiral ridgethereabout, to promote a spiral pattern of water flow through thepassageway for better heat transfer.

The heat pump water heater also preferably includes a water outlet pipeby which heated water is removed from a top portion of the water tank.Then, there is provided a water inlet pipe by which water to be heatedis introduced into the water tank. This water inlet pipe includes anoutlet in the water tank which is inside of the inner sleeve andvertically adjacent to the bottom opening of the inner sleeve. Morepreferably, the outlet of the inlet pipe directs the introduced waterdownwards towards the bottom opening of the inner sleeve.

Various bottom openings of the inner sleeve are possible, including onewhich is flared downwardly and outwardly, one which is flared downwardlyand inwardly, and one which is flared straight downwardly.

If desired, the inner sleeve includes a spiral ridge on an insidesurface thereof.

One aspect of this invention is that the passageway between the outerwater tank and inner sleeve will cause the water to remain in closer andlonger contact with the heated wall of the water tank. This contactresults in transferring of more heat to the water in the passagewaybetween the heated wall of the water tank and the inner sleeve,increasing the heat transfer and efficiency over a traditional coiltank.

Another aspect of this invention is that it causes the heated water tobe separated from the rest of the water in the water tank duringheating, thus providing the hottest water to the hot water outlet whenit is located (as usual) at the top portion of the water tank (eithercentrally or at upper sides of the water tank near the top).

Another aspect of this invention is that the water that is heated in thepassageway between the outer water tank and the inner sleeve is alwaysconvecting upward to the top of the water tank where the hot wateroutlet is preferably located, while at the same time the (relatively)cooler water located at the top of the water tank is thus displaced andflows downward to start the heating cycle of that cooler water again.

Another aspect of this invention is that the heated water concentratedbetween the outside wall of the water tank and the inner sleeve willcreate convection causing: a) the heated water to rise to the top of thewater tank, b) the cooler water at the top of the water tank tocirculate downward into the cavity inside of the inner sleeve, c) thecooler water to convect down and pass through the opening in the bottomof the horizontal or curved bottom of the inner sleeve, and d) thecooler water to be convected upward between the water tank and innersleeve to effect a rapid heating of the cooler water. This thuscompletes a circulatory cycle of the hot and cooler water, causing thewater to be heated more efficiently in the space or passageway betweenthe outer water tank and inner sleeve.

Another aspect of this invention is that the opening in the bottom ofthe inner sleeve allows the cooler water in the tank to be drawn downthrough this opening as the heated water in the space between the outertank and inner sleeve is heated and rises, causing the cooler water tocirculate downward. The bottom of the inner sleeve can be flat or curvedas to cause the cooler water to easily enter the opening and beconvected outward and upward passing through the passageway between theouter tank and inner sleeve.

Another aspect of this invention is that the bottom opening of the innersleeve can be of any size and have any number of openings to improve theconvection flow. This bottom opening can also have a collar to theconcave or convex side to improve the flow of the cold water through theopening.

Another aspect of this invention pertains to an improvement over thetraditional inside refrigerant coil heating method. Traditional waterheaters have different types of heating elements inside the tank. Theseelements are susceptible to erosion, calcification and generaldissolution. Copper heat transfer coils inside a potable water tank areknown to attract minerals, to become calcified, and to have a lessenedefficiency. Although anodic rods are made to prevent corrosion withintanks, these may or may not be used with the heat pump water tank of thepresent invention. These rods are rarely maintained or serviced in atimely manner.

Other features and advantages of the present invention are stated in orapparent from detailed descriptions of presently preferred embodimentsof the invention found hereinbelow.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross sectional elevation view of a heat pump water heaterof the present invention.

FIG. 2 is a cross sectional top view of the heat pump water heaterdepicted in FIG. 1.

FIG. 3 is a broken out portion of the water tank wall depicted in FIG.1.

FIG. 4 is an elevation view of an alternative water sleeve of thepresent invention.

FIG. 5 is a cross sectional elevation view of a second alternative watersleeve of the present invention.

FIG. 6 is a cross sectional elevation view of a third alternative watersleeve of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawings in which like numerals represent likeelements throughout the views, there is disclosed in FIGS. 1 and 2 aheat pump (hereafter HP) water heater 10 according to the presentinvention. HP water heater 10 includes a cylindrical water tank 12 wherepotable water 14 is heated and stored. Water tank 12 can be of anyshape, although a rounded end cylindrical shape is usually the mosteffective, and preferably water tank 12 includes insulation 15thereabout as shown. Water tank 12 can also be manufactured out of anynumber of suitable materials including, but not restricted to: stainlesssteel, galvanized steel, ceramic coated steel, or plastic. Generally,water tank 12 is provided with a water inlet pipe 16 for the water to beheated and a water outlet pipe 18 to enable the hot water 14 in watertank 12 to be withdrawn for use. Water tank 12 can further contain anynumber of access openings for any number of accessories such as, but notlimited to, a temperature sensor 20 and an auxiliary heating element 22.

Conveniently, a suitably driven heat pump 24 is located in a housing 26provided on top of (or otherwise adjacent to) water tank 12. Housing 26has an air inlet 28 and an air outlet 30 positioned and sized as needed.Heat pump 24 circulates a working fluid or refrigerant via a hot outlettube 32 and a cold return tube 34.

In accordance with the present invention, a spiral tubing 40 forcirculating heated refrigerant from hot outlet tube 32 and back to coldreturn tube 34 is placed in contact with the outer wall of tank 12.Tubing 40 is conveniently round, but can be flat or oval for to providea greater heat transfer surface area. As shown in FIG. 1, this contactof tubing 40 is preferably accomplished by putting tubing 40 in a spiralgroove 42 located around the outside surface of tank 12, thus providinga large surface area for good heat transfer. Tubing 40 is at leastinside of insulation 15. Tubing 40 is also preferably formed into coilslocated in grooves 42 around the bottom of water tank 12 as shown inFIG. 1, and from which the cooled refrigerant is fluidly connected tocold return tube 34. The coils of tubing 40 can also be coated with acoating 44, as shown best in FIG. 3, which will more readily effect heattransfer from the coils to the material of water tank 12 and thus towater 14. Coating 44, or a separate (different) protective coating, mayalso be used to create a barrier between water tank 12 and tubing 40 toavoid any electrolytic reaction between tubing 40 and water tank 12 thatwould otherwise cause corrosion of either material.

HP water heater 10 of the present invention also includes an innercylindrical sleeve 46 manufactured out of metal, ceramic or plastic thatpreferably follows the general contours of the inside of tank 12.Although inner sleeve 46 can be made out of any number of materials,these materials must be safety approved for use with potable water alongwith all of the other components of HP water heater 10. In addition,inner sleeve 46 preferably (but not necessarily) has an insulatingvalue, in order to allow heated water 14 on the outside thereof (inpassageway 48 as noted below) to more efficiently retain the heattransferred thereto by tubing 40 as water 14 moves convectively upward,otherwise some of that heat would be lost through contact with innersleeve 46 and to the cooler water 14 traveling downward there through.It will be appreciated that inner sleeve 46 is spaced from the adjacentportions of water tank 12 by suitable braces 49 or the like, whichspacing creates a separation passageway 48 between the side and bottomsurfaces of water tank 12. With the provision of passageway 48, water 14therein can naturally circulate via convection as shown by arrows 50,and water 14 to be heated therein is kept in close contact with the heattransferring wall of tank 12 for a more efficient transfer of heat towater 14. The top of inner sleeve 46 is open as shown, while the bottomof inner sleeve 46 can be bowed outwardly or concave (as shown). Ofcourse, the bottom of inner sleeve 46 could also be bowed inwardly orconvex, or flat as desired. At the bottom of inner sleeve 46 there isprovided an outlet opening 52 which is flared outwardly in thisembodiment and through which water 14 in water tank 12 flows as shown byarrows 50. A plurality of bottom openings of inner sleeve 46 would alsobe possible if desired.

There is also provided, through the side of water tank 12 and throughthe side of inner sleeve 46, an inlet pipe 54 for cold make-up or supplywater to be added to water tank 12. Preferably, inlet pipe 54 ispositioned near the bottom surface or lower side of inner sleeve 46, sothat water flowing into water tank 12 is close to outlet opening 52 andhence so that the (cooler) water from water inlet pipe 16 will beimmediately drawn down through outlet opening 52 and enter intopassageway 48 to be heated immediately and before substantial mixingwith the remaining (hot) water 14 in water tank 12. Alternatively, aninlet pipe 16′ can be positioned so that the cold water enterspassageway 48 directly and preferably at the bottom thereof (as shown inFIG. 4), rather than through outlet opening 52. Inlet pipe 16 can alsohave an outlet (as shown in FIG. 4) which directs the incoming (cold)water in the direction of outlet opening 52, to more efficiently causethe incoming (cooler) water therefrom to flow down through outletopening 52 and into that part of passageway 48 at the bottom of innersleeve 46. From the bottom of water tank 12, it will be appreciated thatthe (cooler) water 14 in passageway 48 is immediately heated by tubing40, and thus flows by convection upwardly in water tank 12. This upwardflow is an efficient way to heat water 14, since water 14 to be heatedis contained in passageway 48 for the entire height thereof (i.e.,between inner sleeve 46 and the wall of water tank 12) to achieve amaximum contact of water 14 with the heated wall of water tank 12 aswater 14 flows by convention upward in passageway 48, with a resultantmaximum heat transfer made to water 14 in passageway 48.

It will be appreciated that water outlet pipe 18 of water tank 12 islocated near the top of water tank 12 or in the side of water tank nearthe top, where the hottest water 14 will be located (via convectionthereof) and consequently then drawn out for use. It will also beappreciated that the design of passageway 48 between water tank 12 andinner sleeve 46 is such that passageway 48 will discourage the (cooler)water from inlet pipe 16 from mixing with the freshly heated (andhottest) water 14 in passageway 48 rising to the top of water tank 12.Of course, if there were mixing of the cooler water first, this couldresult in an undesirable lowering of the overall temperature of water 14throughout water tank 12, and in particular at the top of water tank 12near outlet pipe 18. Instead, the configuration of water tank 12 keepsthe supply of the hottest water 14 in water tank 12 flowing at all timesto the top, and with the cooler water 14 being heated first during anyheating cycle.

An alternative inner sleeve 60 for inner sleeve 46 of HP water heater 10is depicted in FIG. 4. Inner sleeve 60 includes a spiral ridge or spacer62 on the outer surface thereof which can be used to maintain innersleeve 60 with a desired or proper spacing from the inside surface ofwater tank 12 (not shown) in place of braces 49. Due to the spiralorientation of ridge or spacer 62 around inner sleeve 60, ridge orspacer 62 can also (or without any spacing utility) be utilized topromote the flow of water. 14 spirally in passageway 48 (the spacebetween inner sleeve 46 and water tank 12) and hence to cause water 14to circulate spirally around passageway 48. Such a spiral flow inpassageway 48 effects more heat transfer due to a longer (spiral) travellength/time while being heated by tubing 48 and the adjacent heatedportions of water tank 12 and inner sleeve 60. As noted above, waterinlet pipe 16′ can also be used as shown to additionally (or by itself)promote the spiral flow of water 14.

A second alternative inner sleeve 70 is depicted in FIG. 5. As shown,inner sleeve 70 has an outlet opening 72 which is straight down. Inaddition, it will be noted that water inlet pipe 74 has a downwardlydirected outlet end 76 which directs the water exiting therefromdirectly down through outlet opening 72 and hence immediately into thesurrounding passageway.

A third alternative inner sleeve 80 is depicted in FIG. 6. As shown,inner sleeve 80 has an outlet opening 82 which is flared inwardly at thelower end thereof. In addition, it will be noted that a spiral ridge 84can similarly be placed on the inside surface of inner sleeve 80 asshown to facilitate a circulation or downward flow of (cold) water 14 toimprove initial circulation.

While the present invention has been described with respect to exemplaryembodiments thereof, it will be understood by those of ordinary skill inthe art that variations and modifications can be effected within thescope and spirit of the invention.

1. A heat pump water heater comprising: a heat pump which supplies a hotrefrigerant; a water tank in which water to be heated is contained, saidwater tank including a lower portion defined by a bottom wall and asurrounding wall extending upwardly from said bottom wall; an innersleeve located in said lower portion of said water tank, said innersleeve being spaced from said bottom wall and an adjacent portion ofsaid surrounding wall whereby a passageway is provided about said innersleeve, said inner sleeve also including an opening at a bottom thereof;and a circulation system by which the heated refrigerant from said heatpump is put in a heat exchange relationship with the water in saidpassageway, causing heating of the water in said passageway and, due tonatural convection, movement of the heated water to a higher position insaid water tank and a resultant flow of cooler water into saidpassageway through said bottom opening of said inner sleeve.
 2. A heatpump water heater as claimed in claim 1, wherein said circulation systemincludes tubing which receives the hot refrigerant from said heat pump,said tubing being disposed on an outside surface of said water tank toheat the water in said passageway.
 3. A heat pump water heater asclaimed in claim 2, wherein said water tank further includes grooves inthe outside surface of the adjacent portion of said surrounding wall ofsaid water tank in which said tubing is at least partially located.
 4. Aheat pump water heater as claimed in claim 3, wherein said tubing isdisposed in a spiral pattern in said grooves on the outside surface ofthe adjacent portion of said surrounding wall of said water tank.
 5. Aheat pump water heater as claimed in claim 2, wherein said tubingincludes an outer heat transfer promoting covering.
 6. A heat pump waterheater as claimed in claim 5, wherein said tubing includes an outerprotective covering.
 7. A heat pump water heater as claimed in claim 1,wherein said inner sleeve includes a spiral ridge thereabout.
 8. A heatpump water heater as claimed in claim 1, and further including: a wateroutlet pipe by which heated water is removed from said water tank; and awater inlet pipe by which water to be heated is introduced into saidwater tank, said water inlet pipe including an outlet in said water tankwhich is inside of said inner sleeve and vertically adjacent to saidbottom opening of said inner sleeve.
 9. A heat pump water heater asclaimed in claim 8, wherein said outlet of said inlet pipe directs theintroduced water downwards towards said bottom opening of said innersleeve.
 10. A heat pump water heater as claimed in claim 1, wherein saidbottom opening of said inner sleeve is flared downwardly and outwardly.11. A heat pump water heater as claimed in claim 1, wherein said bottomopening of said inner sleeve is flared downwardly and inwardly.
 12. Aheat pump water heater as claimed in claim 1, wherein said bottomopening of said inner sleeve is flared straight downwardly.
 13. A heatpump water heater as claimed in claim 1, wherein said inner sleeveincludes a spiral ridge on an inside surface thereof.
 14. A heat pumpwater heater comprising: a heat pump which supplies a hot refrigerant; acylindrical water tank in which water to be heated is contained, saidwater tank including a surrounding wall and a bottom wall and having alower portion; a cylindrical inner sleeve located in said lower portionof said cylindrical water tank, said inner sleeve being spaced from saidbottom wall and an adjacent portion of said surrounding wall whereby acylindrical passageway is provided about said inner sleeve, said innersleeve also including an opening at a bottom thereof; and a circulationsystem by which the heated refrigerant from said heat pump is circulatedalong the surrounding wall of said water tank and hence put in a heatexchange relationship with the water in said passageway, causing heatingof the water in said passageway and, due to natural convection, movementof the heated water to a higher position in said water tank and aresultant flow of cooler water down through said inner sleeve and intosaid passageway through said bottom opening of said inner sleeve.
 15. Aheat pump water heater as claimed in claim 14, wherein said circulationsystem includes tubing which receives the hot refrigerant from said heatpump, said tubing being disposed on an outside surface of said watertank to heat the water in said passageway.
 16. A heat pump water heateras claimed in claim 15, wherein said water tank further includes groovesin the outside surface of the adjacent portion of said surrounding wallof said water tank in which said tubing is located.
 17. A heat pumpwater heater as claimed in claim 16, wherein said tubing is disposed ina spiral pattern in said grooves on the outside surface of the adjacentportion of said surrounding wall of said water tank.
 18. A heat pumpwater heater as claimed in claim 17, wherein said inner sleeve includesa spiral ridge thereabout.
 19. A heat pump water heater as claimed inclaim 16, and further including: a water outlet pipe by which heatedwater is removed from said water tank; and a water inlet pipe by whichwater to be heated is introduced into said water tank, said water inletpipe including an outlet in said water tank which is inside of saidinner sleeve and vertically adjacent to said bottom opening of saidinner sleeve.
 20. A heat pump water heater as claimed in claim 19,wherein said inner sleeve includes a spiral ridge on an inside surfacethereof.